1. Field of the Invention
The present invention relates generally to thermally conductive, electrically insulative multi-layer laminae for mounting printed circuits and the surface mounting of semiconductor devices connecting to such circuits. More particularly, the invention relates to heat dissipation in a recessed dual-sided, back-to-back mounting arrangement adapted for use with a thermally conductive support board or mounting base to increase circuit density without increasing chassis size. The mounting system may be further provided with shaped recesses adapted to receive multi-layer semiconductor mounting laminae of matching pattern for insertion in a lock-in type mode to the thermally conductive support board or mounting base in precise relation to surface circuits.
2. Description of the Related Art
A solid-state electronic device is normally mounted on a support member which, in turn, is received in the chassis of the larger apparatus to which it pertains. The support member is thermally conductive, but electrically insulating, to the chassis. The electronic devices operatively mount on the surface of the support member and are electrically coupled to printed circuitry, and other devices. These include surface mounted resisters and/or leadless chip carriers having one or more chip assemblies which may be received on the surface of the circuit-bearing layer. It is also known to provide a multi-layer laminate incorporating a metallic base or substrate circuit carrying layer with one or more distinct electrically insulative and thermally conductive layers being disposed therebeneath and one or more conductive metal or heat spreader layers frequently being interposed beneath or between the insulative layers. The printed circuit carrying layer or surface mounting layer for semiconductor devices is the outer surface of the base member or circuit board device.
Heat generated by electrical devices in circuit arrangements has long been a limiting factor in the ability of designers to reduce the size of the circuits in complicated electrical or electronic devices because of heat dissipation limitations. Therefore, increased heat dissipation has long been a desirable goal in the development of such circuitry. Accordingly, each development which allows such devices to dissipate heat more efficiently, as by overcoming thermal impedance in electrically insulating materials without reducing the electrical insulating properties of that material, for example, is highly desirable.
One such arrangement is illustrated and described in U.S. Pat. No. 4,810,563 issued Mar. 7, 1989, entitled "Thermally Conductive, Electrically Insulative Laminate". That application is assigned to the same assignee of the present invention. That invention represents a distinct improvement in the state-of-the-art ability of mounting devices to dissipate heat generated by the electrical circuit elements including any semiconductor devices mounted thereon. The use of the circuit mounting techniques and arrangements described in the reference show excellent heat dissipation for single layer circuit arrangements. However, such arrangements limit the number of layers of circuitry which can be mounted in a given volume of chassis space. The increased sophistication and miniaturization of devices has made it highly desirable that all the available space be utilized to the degree that heat dissipation allows. Thus, dual sided arrangements would enhance this situation a great deal.
In addition to maximizing heat dissipation, the simplification of assembly with respect to positioning and mounting laminated elements in the support or base member and making the necessary connections has long been sought by circuit manufacturers. Ease of placing and connecting recessed laminar elements in situ is a prominent factor associated with both reduced cost and increased reliability of finished parts.